Attention is hereby directed to U.S. patent application Ser. No. 08/297,200 (D/94226) entitled xe2x80x9cPuzzle Cut Seamed Beltxe2x80x9d, now U.S. Pat. No. 5,514,436, issued May 7, 1996; U.S. patent application Ser. No. 08/297,158 (D93563) entitled xe2x80x9cPuzzle Cut Seamed Belt With Strength Enhancing Stripxe2x80x9d, now continuing U.S. patent application Ser. No. 08/522,622, filed Aug. 31, 1995; U.S. patent application Ser. No. 08/297,201 (D/94225) entitled xe2x80x9cPuzzle Cut Seamed Belt With Bonding Between Adjacent Surface By UV Cured Adhesivexe2x80x9d, now U.S. Pat. No. 5,487,707, issued Jan. 30, 1996; U.S. patent application Ser. No. 08/297,206 (D/94226Q) entitled xe2x80x9cEndless Seamed Belt with Low Thickness Differential Between the Seam and the Rest of the Beltxe2x80x9d, allowed, but not yet issued; and U.S. patent application Ser. No. 08/297,203 (D/94227) entitled xe2x80x9cPuzzle Cut Seamed Belt with Bonding Between Adjacent Surfacesxe2x80x9d, all commonly assigned to the assignee of the present invention and filed on Aug. 29, 1994.
This invention relates generally to a process and apparatus for producing an endless seamed belt, and more particularly concerns the configuration of the die press components used to cut a flexible seamless belt with interlocking patterned ends.
Initially, belts were fabricated by taking two ends of a web material and fastening them together by a variety of techniques such as sewing, wiring, stapling, providing adhesive joints, etc. While such joined or seamed belts are suitable for many applications, such as the delivery of rotary motion from a source such as a motor, to implement a device such as a saw blade, they are not as satisfactory in many of the more sophisticated applications of belt technology in common practice today. In the technology of the current day many applications of belts require much more sophisticated qualities and utilities and in particular for such special applications as in electrostatographic and electrographic imaging apparatus and processes for use as photoreceptors, intermediate sheet and/or image transport devices, fusing members or transfix devices it is ideal to provide a seamless belt whereby there is no seam in the belt which mechanically interferes with any operation that the belt performs or any operation that may be performed on the belt. While this is ideal the manufacture of seamless belts requires rather sophisticated manufacturing processes which are expensive and are particularly more sophisticated, difficult and much more expensive for the larger belts. As a result, various attempts have been made to provide seamed belts which can be used in these processes. Previous attempts to manufacture seamed belts have largely relied on belts where the two ends of the belt material have been lapped or overlapped to form the seam or have butted against one another and then fastened mechanically by heat or other means of adhesion such as by the use of an adhesive or ultrasonic welding.
The belts formed according to the typical butting technique while satisfactory for many purposes are limited in bonding, strength and flexibility because of the limited contact area formed by merely butting the two ends of the belt material. Furthermore, belts formed according to the butting or overlapping technique provide a bump or other discontinuity in the belt surface leading to a height differential between adjacent portions of the belt, of 0.010 inches or more depending on the belt thickness, which leads to performance failure in many applications. For example, one of the most severe problems involves cleaning the imaging belt of residual toner after transfer of the toner image. Intimate contact between the belt and cleaning blade is required. With a bump, crack or other discontinuity in the belt the tuck of the blade is disturbed which allows toner to pass under the blade and not be cleaned. Furthermore, seams having differential heights may when subjected to repeated striking by cleaning blades cause the untransferred, residual toner to be trapped in the irregular surface of the seam. Furthermore, photoreceptors which are repeatedly subjected to this striking action tend to delaminate at the seam when the seam is subjected to constant battering by the cleaning blade. As a result, both the cleaning life of the blade and the overall life of the photoreceptor can be greatly diminished as well as degrading the copy quality. In addition, such irregularities in seam height provide vibrational noise in xerographic development which disturb the toner image on the belt and degrades resolution and transfer of the toner image to the final copy sheet. This is particularly prevalent in those applications requiring the application of multiple color layers of liquid or dry developer on a photoreceptor belt, which are subsequently transferred to a final copy sheet. In these applications, it is desired to provide a seam height differential between the seam and the unseamed adjacent portions less than 0.001 inch. In addition, the presence of the discontinuity in belt thickness reduces the flex life and continuity of strength of the belt which for prolonged use is desirably 80-90% that of the parent material unseamed. In addition, the discontinuity or bump in such a belt may result in inaccurate image registration during development, inaccurate belt tracking and overall deterioration of motion quality, as a result of the translating vibrations.
An endless seamed belt can be formed with patterned interlocked ends, the pattern of the ends being formed by using a laser or a die to cut the pattern and the patterned cut ends being brought together to interlock to form a seam. In experiments the patterned seams were first generated using a CO2 laser programmed to make various patterned node sizes and spacings. The laser was an excellent tool for quickly changing geometries and conditions, however it was a costly and timely process and an inappropriate process for manufacturing seams for large volumes of belts. A 1 inch length punch press die was designed to cut small belt seam samples for testing purposes. The die cut is much faster and cleaner than the laser cut and the die cut was determined to be the preferred method to be used in the patterned seam belt manufacturing process. However, the size, approximately 0.5 mm, and spacings, approximately 25 microns, of the nodes of the pattern require very accurate cutting by a die and it was thought to be impossible for a die to maintain such demanding tolerances for the width of an operational belt seam.
The following disclosures may be relevant to various aspects of the present invention:
Some relevant portions of the foregoing disclosures may be briefly summarized as follows:
U.S. Pat. No. 1,303,687 teaches forming a container from a body blank with the ends dovetailed together and a covering sheet which extends beyond the end of the body and has its extending portion secured down, overlapping the dovetail joint to secure and finish the container. In forming the container, the body blank is wrapped around a forming mandrel of the desired shape and the two dovetail ends are interlocked. At the same time the extending ends of the covering sheet, which are provided with adhesive, are stuck down overlapping the joint.
U.S. Pat. No. 2,461,859 teaches an endless flexible belt with a patterned dovetail joint. A single die cut may cut both ends of the patterned dovetail joint at the same time. The ends of the belt are cut to form a male and female end with a plurality of spaced dovetailed tabs, the female end fitting into the male end and the dovetailed tabs interlocking with each other. An adhesive may be used at the belt joint.
U.S. Pat. No. 2,792,318 discloses forming splice joints in fibrous material, each joint being cut so that an interlocking tongue and groove pattern is formed. The tongues and grooves may be different shapes. In the finished product, the joints are oriented at a diagonal with respect to the sides. A coating material may be used to maintain the interfitted tongues and grooves, however, it is the interlocking connection of the tongues and grooves that provides the tensile strength of the joint.
U.S. Pat. Nos. 4,878,985 and 5,286,586 disclose fabricating thin flexible endless belts used in electrophotographic printing systems. The patents teach overlapping the ends of the belt and welding the ends together to form an endless belt.
U.S. Pat. No. 4,624,126 teaches a hydraulic press with a cylinder arrangement for equalizing forces in the event of unequal loading of the press.
All of the above references are herein incorporated by reference.
One aspect of the invention is drawn to an apparatus for producing an endless flexible seamed belt from belt material stock including a belt material positioner which positions the belt material stock for cutting; a die assembly including a die with a first die cutting edge having a first die pattern; a punch assembly including a punch with a first punch cutting edge having a first punch pattern that is complementary to the first die pattern; and a force generating assembly which generates a cutting force in a cutting operation in which the punch and die cut the belt material so that a first patterned end is formed on a first end of the belt and a second patterned end is formed on a second end of the belt, wherein the first and second patterned ends of the belt are cut in a puzzle cut pattern with mutually mating elements which fit together to form a seam when joined mechanically to enable the endless flexible seamed belt to essentially function as an endless belt having a substantially uniform thickness.
Another aspect of the invention is drawn to a method of making an endless flexible seamed belt from belt material stock including positioning the belt material stock between a die assembly and a punch assembly, the die assembly including a die with a first die cutting edge having a first die pattern and the punch assembly including a punch with a first punch cutting edge having a first punch pattern that is complementary to the first die pattern; applying a cutting force from a force generating assembly to a force receiving surface on the punch assembly so that the die and punch cut the belt material to form a first patterned end on a first end of the belt and a second patterned end formed on a second end of the belt; and removing the cutting force from the punch assembly, wherein the first and second patterned ends of the belt are cut in a puzzle cut pattern with mutually mating elements which fit together to form a seam when joined mechanically to enable the endless flexible seamed belt to essentially function as an endless belt having a substantially uniform thickness.
In a manufacturing mode, it is desirable to have a fast and accurate method of forming the puzzle cut seam design. Using a die to cut the flexible belt material is much quicker than using a laser to form the puzzle cut seam. The die cut is also cleaner than the laser cut due to the fact that the laser melts the belt material, which is a particular problem in a multi-layered belt. Having a clean puzzle cut seam is very important when the belt is used in an electrophotagraphic machine environment due to the very small distances between the electrophotagraphic process elements and the belt. A special die with a tolerance of 0.0002 inch runout in a 60 inch linear plane was designed and fabricated to cut the small nodes and spacings of the puzzle cut seam. In order to maintain the close tolerances of the patterned cutting edges of the die, a novel die press and method of using the die had to be invented. The die is formed so that the back end of one belt is formed in the same punch as the front end of another belt. This results in a small area of waste material between the two ends, however the time and energy saved in placing and cutting the two ends independently far outweigh the cost of the waste material.